1. Technical Field
The present invention relates to a method for manufacturing a water resistant aluminum pigment dispersion, a water resistant aluminum pigment, and an aqueous ink composition containing the same.
2. Related Art
Heretofore, as a method for forming a coating film having a metallic gloss on a printed material, for example, a method using a printing ink in which a gold powder or a silver powder formed, for example, from a brass or an aluminum fine powder is contained as a pigment, a foil press printing method using a metal foil, or a thermal transfer method using a metal foil may be mentioned.
In recent years, many applications of ink jet techniques have been performed in printing fields, and as one of the applications, metallic printing may be mentioned, so that development of an ink having a metallic gloss has been carried out. For example, in JP-A-2008-174712, an aluminum pigment dispersion containing an organic solvent, such as an alkylene glycol, as a basic component and a non-aqueous ink composition containing the above dispersion have been disclosed.
On the other hand, in views of global environmental conservation, safety for human beings, and the like, instead of a non-aqueous ink composition containing an organic solvent as a basic component, development of an aqueous ink composition has been actually desired.
However, when an aluminum pigment is dispersed in water, it generates a hydrogen gas and also forms alumina by reaction with water, and whitening occurs thereby; hence, as a result, the metallic gloss is disadvantageously degraded. Accordingly an ink composition containing an aluminum pigment must be a composition which hardly contains water and which contains an organic solvent as a basic component.